Merge branch 'zobrist'

1 files changed, 2 insertions, 60 deletions

diff --git a/include/negamax.c b/include/negamax.c
index 061b629..cfe2643 100644
--- a/include/negamax.c
+++ b/include/negamax.c
@@ -8,74 +8,15 @@ const float infty = 3.0;
 char negamax_ptn[9];
 uint8_t negamax_search_depth = 3;
 
-static uint64_t *zobrist[15];
-
 // ===================================================================
 // Helpers
 // ===================================================================
 
-static void
-zobrist_free(void);
-
-static int
-zobrist_init(void);
-
-static uint64_t
-zobrist_compute(void);
-
 static float
 negamax(const uint8_t cur_depth, float alpha, float beta,
 				const float colour);
 
 // ===================================================================
-// Zobrist hashing
-// ===================================================================
-
-static uint64_t
-zobrist_compute(void) {
-	uint64_t hash = 0;
-	for (uint8_t l=0; l<board_size*board_size; l++) {
-		colour_stack_t c = colours[l];
-		const uint8_t count = COUNT_AT(l);
-		enum STONE_VARIANT s = STONE_AT(l);
-		for (uint8_t h=0; h<15; h++) {
-			if (h<count) {
-				hash ^= zobrist[h][l*(2*3+1)+(c&1)*3+s];
-				c >>= 1;
-			}
-		}
-	}
-	return hash;
-}
-
-static int
-zobrist_init(void) {
-	for (int k=0; k<15; k++) {
-		if (zobrist[k] != NULL) return EXIT_FAILURE;
-	}
-
-	for (int j=0; j<15; j++) {
-		zobrist[j] = malloc(sizeof(uint64_t)*board_size*board_size*(2*3+1));
-		for (int k=0; k<board_size*board_size*(2*3+1); k++) {
-			XORSHIFT64;
-			zobrist[j][k] = RANDOM64;
-		}
-	}
-
-	return EXIT_SUCCESS;
-}
-
-static void
-zobrist_free(void) {
-	for (int k=0; k<15; k++) {
-		if (zobrist[k] != NULL) {
-			free(zobrist[k]);
-			zobrist[k] = NULL;
-		}
-	}
-}
-
-// ===================================================================
 // α-β negamax using the cnn1986 evaluation function and transposition
 // tables using Zobrist hasing and a treap
 // ===================================================================
@@ -119,7 +60,7 @@ negamax(const uint8_t cur_depth, float alpha, float beta,
 	tt_entry_t *entry = tt_seek(hash);
 
 	// CAUTION: >= breaks search stability
-	if (entry != NULL && entry->depth == cur_depth) {
+	if (entry != NULL && entry->depth >= cur_depth) {
 		if (entry->flag == TT_EXACT) {
 			return entry->value;
 		} else if (entry->flag == TT_LOWERBOUND && entry->value > alpha) {
@@ -145,6 +86,7 @@ negamax(const uint8_t cur_depth, float alpha, float beta,
 	for (action_node_t *node=list->head; node!=NULL; node=node->next) {
 
 		action_take(node->action);
+
 		// Compute the value of the node
 		float node_value;
 		if (ply >= 2*board_size - 2 && (w = check_win()) < 0xFF) {